Face ID first appeared on the iPhone X in 2017. It works thanks to the presence of TrueDepth module in Apple smartphones, which includes a camera, projector and various sensors.
Over the three generations, this sensor has not changed, although the Face ID function is much faster in the new iPhone. But this is the merit of software optimization in the new iOS, not hardware changes.
According to analysts, the upcoming generation of iPhone will finally receive an updated TrueDepth module. There are no details, but such rumors have already appeared and they concerned a reduction in the size of sensors and an increase in system performance in general. So the iPhone 12 can really get smaller cutouts in the screens and an even faster Face ID feature.